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Abstract: The definition of a cumulant detector of an arbitrary order of non-Gaussian signals against the background of non-Gaussian interferences is introduced, and its sensitivity coefficient is determined. Dependenci... PubDate: 2025-06-05
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Abstract: This paper proposes an approach to infrared image enhancement involving iterative wrapping of the enhancement core within an image upscale/downscale loop. It highlights and suppresses distortion and blurs fine... PubDate: 2025-06-05
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Abstract: In the first part of the paper, analytical relations are obtained to calculate the plasma boundary position relative to the cathode surface in the high-voltage glow discharge electrode system forming a ribbon ... PubDate: 2025-06-05
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Abstract: This study presents a two-stage differential amplifier circuit that has been improved for use in a realistic biomedical signal conditioning system. CMOS technology serves as the foundation for the circuit. A M... PubDate: 2025-06-05
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Abstract: Coating metal surfaces with liquid foams is a promising approach to reducing microwave reflectivity. Due to disintegration processes, liquid foams quickly change their properties over time. The objective of th... PubDate: 2025-06-05
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Abstract: Abstract The necessity to increase kamikaze drones’ efficiency and to reduce their cost is caused by their significant prevalence. In this sense, it is necessary to equip such unmanned aerial vehicles (UAV) with inexpensive thermal image cameras. The target detection range and recognition with a given probability are principal consumer evaluations for remote surveillance thermal image systems. Currently, in this case, using microbolometric matrix detectors with inexpensive infrared lenses is the best technical solution. The calculation method is advisable to justify the lens parameters compatible with the selected detector and ensure maximum operational efficiency. The article is devoted to the simplified synthesis method for developing the main parameters of the UAV thermal image system lens for the chosen type of microbolometric matrix detector. The methodology is based on the noise equivalent temperature difference. Based on the proposed method, a calculation example of a lens for an inexpensive on-board thermal imager of a kamikaze drone is given. PubDate: 2024-05-01
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Abstract: Abstract The paper investigates the influence of the choice of weighting coefficients on the formation of quadrature components in I/Q demodulators. It proposes methods to improve the accuracy of I/Q demodulation and minimize quadrature errors. Different configurations of 8- and 10-sample I/Q demodulators with open sets of weighting coefficients are considered. Using simulation, it has been shown that certain sets of coefficients can significantly improve the amplitude-frequency characteristics, achieving a bandwidth narrowing of 1.5–1.7 times and better suppression of out-of-band interference. The synthesis of new sets of coefficients for 10-sample I/Q demodulators is also investigated, which leads to improved amplitude-frequency characteristics and reduced phase errors. The equivalence between combinations of two-stage demodulators and their single-stage counterparts is established, providing potential computational efficiency advantages. The proposed 13- and 15-sample equivalent filters demonstrate a high frequency filtering efficiency and zero orthogonalization error, making them a promising alternative to 16-sample demodulators. The obtained results emphasize the importance of choosing weighting coefficients to optimize the performance of I/Q demodulators and contribute to developing more accurate and efficient digital communication systems with increased noise immunity. PubDate: 2024-05-01
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Abstract: Abstract This article unveils a cutting-edge methodology for Fetal Phonocardiogram (FPCG) classification employing Bidirectional Long Short-Term Memory (BiLSTM) networks. Acknowledging the pivotal role of fetal heart monitoring in early anomaly detection, the research delves into the profound insights offered by FPCG signals concerning fetal cardiac activity. The innovative approach encompasses preprocessing FPCG signals using Mel-Frequency Cepstral Coefficients (MFCC) and spectrogram features, coupled with the strategic application of BiLSTM networks, ensuring a resilient classification framework. The bidirectional nature of the LSTM architecture elevates the model’s ability to capture temporal dependencies in both forward and backward directions, facilitating the discernment of intricate patterns in fetal heart sounds. Experimental findings demonstrate a 98% accuracy, reaffirming the effectiveness and precision of the BiLSTM approach in FPCG classification. This research significantly advances automated methods for evaluating fetal cardiac health, promising transformative enhancements in prenatal care. PubDate: 2024-05-01
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Abstract: Abstract The paper proposes a narrow-band polarization plane filter-rotator in a circular waveguide with minimal longitudinal dimensions (~λ/30) and a 2–3% bandwidth at a return loss level of 20 dB in the center of a double-humped passband. The rotator consists of two closely spaced irises, each with a single centered rectangular slot. In contrast to rotators with rotational symmetry Cn of order n > 2, which rotate an incoming linearly polarized wave by the same angle irrespective of its polarization direction, the proposed device allows us to rotate a wave polarized orthogonally to the wide wall of the rectangular slot of the first iris. The possibility of rotation at any angle slightly less than 90° is demonstrated. The polarization plane’s rotation angle differs from the second iris’s rotation angle by fractions of a degree. Therefore, the design of the device allows us to use an intuitive synthesis algorithm. The mutual influence and permutation of the complex eigenfrequencies of the meta-cell from a pair of single-slot irises explain the double-humped AFC. The device can provide a smooth mechanical adjustment of the polarization plane within ±14° with good matching by rotating the second iris around its axis. We used our implementation of the mode-matching techniques and the method of generalized scattering matrices for the calculations. PubDate: 2024-05-01
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Abstract: Abstract The modern development of information and communication systems (ICS) in the context of the widespread use of radio signals with statistical and dynamic characteristics close to those of white noise requires new approaches to the correct decision-making on the natural or artificial character of the process observed during the electronic intelligence. In this paper, we propose to use the SG (Savit and Green) predictability index to classify the processes used in ICS. With the help of the proposed identification scale, which uses SG index as a parameter, the processes are analyzed and conventionally divided into three classes: IID-processes, chaotic processes with a destructured image in pseudo-phase space (IPPS), chaotic processes with a structured IPPS, and periodic processes. For each process, a histogram of the distribution of SG values on the identification scale is plotted. Based on the conducted analysis, it was established that the identification scale based on the SG value effectively distinguishes not only classes of processes (for example, random, chaotic, and deterministic), but also processes within individual classes, for example, it distinguishes chaotic processes with destructured and structured IPPS. The results demonstrate statistical significance and reliability of the new classification method, making it promising for use in real ICS. PubDate: 2024-05-01
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Abstract: Abstract The paper presents a nonparametric method for joint estimation of the delay time and Doppler factor of a pseudo-randomly phase-shift keying signal under a priori uncertainty about the probability distribution law of the white multiplicative interference in its observation. When estimating the signal parameters, the Doppler deformation of the envelope and shift of the carrier frequency are considered. The problem of estimating the signal delay time at a known Doppler factor is studied separately. The parameter estimation problem is investigated, assuming that the noise component is a process with independent and identically distributed random quantities (white noise). The proposed method minimizes the goal function that uses observing BDS statistics. The delay time and the Doppler factor are determined by calculating the minimum value of the goal function of the mismatch between the observed signal and its model under conditions of joint variation of parameters. Properties of joint nonparametric estimates of the signal delay time and the Doppler factor obtained for different parameters of the BDS statistics have been investigated. There are presented dependences of mathematical expectations and mean square errors of joint estimates of the delay and Doppler factor of the received signal for several probability density distributions at different parameters of the multiplicative interference scale, including those with heavy tails. Using statistical simulation, it has been shown that the proposed method makes it possible to obtain acceptable estimates of signal parameters under a priori uncertainty about the distribution of multiplicative interference. PubDate: 2024-04-01
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Abstract: Abstract The paper presents the results of research on the creation and development of radiation sources in the frequency range of 100–400 GHz using silicon (Si) avalanche diodes (ADs). Effective frequency converters of highly stable low-frequency signals with a level of 10–30 mW output microwave power of continuous radiation are proposed and implemented. The minimal circuit losses and maximum output power of ADs, which have a low impedance, are achieved in the oscillating system on an open radial line. The equivalent circuits of generators are considered and electrophysical parameters of avalanche structures are provided. Design schemes of radiation sources and their main parameters are also presented. The use of such radiation sources makes it possible to implement qualitatively new promising applications in this frequency range, in particular, to obtain high-resolution images of targets, to achieve transmission rates of up to 100 Gb/s and more, to study in detail properties of materials, and the structure of the universe. PubDate: 2024-04-01
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Abstract: Abstract In this article, using the inverse problem method, an analysis of a third-order bandpass filter (triplet BPF) with all mixed couplings was carried out. These filters have advantages over simpler triplet BPFs with partially used mixed couplings. The inverse problem method determines the mixed coupling coefficients of a triplet BPF from a given location of two transmission zeros (TZ) on the complex plane s = σ + jΩ. As a result of the analysis, it was found that triplet BPFs with all mixed couplings more effectively bring together TZs located on the σ or jΩ axis, which leads to an increase of flat group delay or BPF selectivity. Microstrip triplet BPFs with all mixed couplings use stepped-impedance resonators (SIR) located a short distance from each other. This results in very compact filters formed according to the “close-packed” principle. In such microstrip filters, increasing the thickness of the dielectric substrate makes it possible to increase the unloaded quality factor Qu of the resonator and realize narrow passbands without increasing the area occupied by the filter. A universal microstrip triplet BPF with all mixed couplings is considered. It combines the properties of symmetric and asymmetric triplet BPF and provides 10 different locations of two TZs on the s-plane and forms significant variety of frequency responses. PubDate: 2024-04-01
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Abstract: Abstract The review analyzes Ukrainian scientists’ achievements in measurements in the microwave and terahertz ranges of electromagnetic waves. The application of ultrashort ultrawideband pulses for subsurface probing and object detection is considered. Such instrumentation tools have practical application in the long-wave part of the microwave range. In the centimeter and millimeter ranges, the method of synthesizing time signals based on multifrequency measurements is promising, and a pulse duration of 70 ps was achieved. The performed synthesis is based on the principle of the Fourier holography in the frequency-time domain, and methods of the parametric spectral analysis are used to obtain signals in the time domain. Some devices are based on the Michelson interferometer idea, which is implemented in a cross of oversized waveguides, the E-plane waveguide cross. Multiprobe meters made it possible to obtain values of the complex reflection coefficient. Such a meter implements the principle of holography on counter-propagating beams in a discrete version. Based on this approach, non-contact vibration meters have been practically implemented. Neural networks found applications for the calibration of detectors and the recognition and estimation of coordinates of objects. Resonance measurement methods are represented by various resonators, such as resonators with “whispering gallery” oscillations, combined open resonators with a short-circuited waveguide section, and coupled biconical resonators. Methods for the physical characterization of liquids in ultra-small volumes of the order of a microliter have been implemented. Such measurements are based on determining the resonant frequency and the quality factor of the mode of oscillations, the determination of which, generally, involves the need to use the fractional rational approximation. Resonance sensors have improved the means of near-field scanning microscopy. Measurements of material properties and nondestructive testing are based mainly on solving the appropriate inverse problem for layered structures. This review presents the research results in this field. PubDate: 2024-04-01
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Abstract: Abstract The paper presents an overview of the authors’ scientific works, which are further developments in the scientific directions of SHF and EHF electronics, which were first developed by scientists, particularly Professor V. P. Taranenko. The possibility of propagation of weakly decaying electromagnetic waves in super dimensional electrodynamic solid-state structures, including those containing plasma-like medium, is demonstrated. Attention is paid to excitation mechanisms of eigenwaves and eigenoscillations of such structures, which are based on the Vavilov–Cherenkov effect, anomalous Doppler effect, or transient radiation. The generation of electromagnetic radiation in the interaction between the charged particle flows, and the fields of eigenwaves or eigenoscillations of such structures have been demonstrated. The possibility of mastering the millimeter and submillimeter wavelength ranges using multimode electrodynamic structures with dimensions acceptable for production is shown. Electrodynamic systems based on supercritical currents of the relativistic electron beam, such as virtod and virtod-BWT, are presented, in which the control of the amplitude-frequency characteristics of microwave radiation is implemented. PubDate: 2024-03-01
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Abstract: Abstract The results of research using 2D simulation in the drift-diffusion approximation of a plasma discharge in a cylindrical dielectric cuvette of 14 mm diameter for a low-pressure induction plasmatron with pumping at a frequency of 2.45 GHz with near-threshold power of 10–25 mW are presented. Spatial distributions of discharge plasma parameters and absorption of electromagnetic energy are calculated. The magnetic field penetrates the plasma to the axis of the cuvette and has a solenoidal behavior with no strong skin effect. The results can be used to develop plasma generators for miniature radio-electronic and gas analytical devices. PubDate: 2024-03-01
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Abstract: Abstract The paper is devoted to considering issues related to the search for ways to create pulse power sources of the terahertz range. It presents the results of mathematical simulation of the energy and impedance characteristics of silicon impact ionization avalanche transit-time (IMPATT) diodes in the frequency range of 200–300 GHz and the elements of matching the impedance of semiconductor structure with the impedance of waveguide transmission line. Based on the calculation results, the diode structures were optimized to attain the maximum microwave power in the pulse mode. Parameters of experimental samples of silicon double-drift IMPATT diodes fabricated with due regard for the data of mathematical simulation are presented. The pulse microwave power of 0.416 W at 233 GHz with a microwave pulse duration of 35 ns has been obtained. PubDate: 2024-03-01
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Abstract: Abstract Results of both theoretical and experimental studies of the beam-wave interaction in compact vacuum electron devices of the clinotron type are presented and discussed. Several modifications to the interaction circuit and radiation output were proposed to improve the performance of clinotron tubes in the sub-THz and THz ranges. These modifications include optimization of the conventional clinotron design to enhance beam-wave interaction and ensure single-mode output radiation in an oversized cavity. Additionally, a new design approach was considered for the THz Cherenkov oscillators and amplifiers, which are based on the excitation of hybrid bulk-surface modes in circuits containing bi-periodic gratings. Theoretical studies were conducted using both “cold” and “hot” simulations with in-house and commercial software. The typical performance of experimental tubes operating in the frequency range of 90 GHz to 410 GHz is presented and compared with the theoretical predictions. Plans for future studies and the developments of THz tubes are also outlined. PubDate: 2024-03-01
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Abstract: Abstract Radioelectronic equipment (REE) for military purposes is used periodically during exercises; at other times, it is stored on a short-term basis. As is known, the failure rate of elements during storage is reduced by 10–100 times compared to the operation of REE, which leads to the accumulation of hidden defects. Therefore, the maintenance and, if necessary, routine repairs are performed before the field deployment. Depending on the storage conditions (open area, under a canopy, unheated or heated storage) and its duration, the number of hidden defects will vary, which affects the time of preparation (repair) of REE before its use. However, this circumstance is not considered in the known methods of quantitative assessment of partial and complex reliability indicators that do not allow us to predict in advance the time required to restore the operability of REE after short-term storage. The paper proposes a method for estimating the average recovery time of REE after short-term storage, and the functional dependencies of reliability indicators on the initial data and controlled variables depending on the quality of metrological and diagnostic support are obtained and studied. The possibility of practical implementation of conditional diagnostic algorithms (CDA) for diagnosing multiple defects with a quantitative assessment of the total number of checks is investigated. The proposed method is formalized as a block diagram of the algorithm, which allows us to predict the average recovery time of REE after the short-term storage, depending on the initial data. Examples of the use and evaluation of the effect of the implementation of the obtained recommendations in the practice of technical operation of REE under actual conditions are presented. This makes it possible to schedule the work of military repair bodies and effectively use their forces and facilities. PubDate: 2024-02-01
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Abstract: Abstract Generators based on unijunction transistors (UJT) are used as sensors of light and magnetic fields, the output parameter of which is generation frequency depending on a measured value. This paper shows experimentally the possibility of a significant increase in sensitivity of such sensors by connecting a bipolar transistor (BT) in a connection variant with an open base in the UJT emitter circuit; the current of this BT is dependent on a light flow and magnetic field. Such a generator based on UJT and BT can be used as a radiation and magnetic field sensor. The UJT can also be applied in industrial optical couplers, where it is an input element with contactless control by the alternation of LED. The possibility of additional contactless control of the optic coupler with an external magnetic field extends their functional possibilities. PubDate: 2024-02-01
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